Cooling fan

ABSTRACT

A cooling fan has a structure to prevent objects from being stuck by the blades of the cooling fan. The cooling fan includes rings spaced from the hub of the cooling fan, that prevent objects from striking the blades while the fan turns. As an alternative, a fan includes ribs radially spaced on the fan blades so as to deflect objects before being struck by the blades.

TECHNICAL FIELD

[0001] The technical field is cooling fans. More specifically, the technical field is cooling fans having structures that reduce the risk of objects being struck by the blades of the cooling fans.

BACKGROUND

[0002] Conventional electrical and electronic components generate considerable heat during operation. Such components are frequently housed in a chassis of a product, which restricts the amount of ambient cooling airflow available to cool the components, resulting in high temperatures within the chassis. High component temperatures are undesirable because high temperatures negatively affect the performance of electrical and electronic components. High temperatures can also damage or shorten the life of components.

[0003] The heat generation problem has grown in significance because of the increased power requirements, and therefore increased heat generation, of modern electrical and electronic components. For example, the processing power of computers has increased dramatically in recent years, which has resulted in higher heat generation from components mounted on computer motherboards.

[0004] A conventional solution to the problem of heat generation is to use cooling fans. Cooling fans are generally effective for cooling electrical and electronic components. However, the rotating blades of cooling fans may pose a danger to objects such as tools, a person's fingers, and other body parts. This problem is of particular concern in consumer electronic products, such as personal computers, where inexperienced owners may access the interior of the products.

[0005] International standards exist to ensure the safety of cooling fans in consumer electronic products. One such standard, IEC/UL/UN 60950, has been adopted by Underwriters Laboratories (UL). IEC/UL/UN 60950 includes a two-part test. Passing either part of the test means that a fan complies with IEC/UL/UN 60950. The first part of the test includes inserting a tool into a suction side of a fan. The tool has a rounded, frustoconical tip. If the tool is not prevented from striking the fans blades by some obstruction, the fan fails the first part of the test. The second part of the test includes inserting a deformable member into the suction side of the fan. The fan passes part two of the test if the fan blade stops rotating under the force of the deformable member before the deformable member strikes a fan blade.

[0006] One conventional approach to complying with IEC/UL/UN 60950 is to place a cage over the suction side of a fan in order to prevent objects from contacting the fan blades. Cages, however, require additional space in the chassis and increase cost.

[0007] Another conventional approach to complying with IEC/UL/UN 60950 is to use low power fans to cool components in a chassis. Low power fans stop more easily when contacted. Low power fans are typically designed to comply with part two of IEC/UL/UN 60950. A disadvantage to this approach is that reducing the power of the fan also reduces the cooling capacity of the fan. Therefore, larger fans, or a greater number of fans, must be used in order to provide a desired cooling capacity for a product housing electronic components. This results in a higher cost to construct the product.

[0008] Therefore, a need exists for a fan for cooling electronic components that does not add undo cost to a product or occupy a large space in a chassis, and that provides adequate cooling for components in the product.

SUMMARY OF THE INVENTION

[0009] Embodiments of the present invention satisfy the above need and may achieve other advantages not present in conventional devices. According to a first aspect, a cooling fan includes a hub, a plurality of blades extending radially outward from the hub, and a first ring intersecting the blades. The first ring may be spaced from the hub a distance of less than about 12 millimeters.

[0010] According to the first aspect, the first ring deflects objects before they contact the leading edges of the blades. The first ring may be constructed as a part of the fan by a molding process. The ring does not require a large space, and does not add undue cost to a product including the cooling fan. In addition, because the ring deflects objects away from the blades, the power of the motor turning the cooling fan does not need to be reduced. Therefore, smaller cooling fans can be used.

[0011] The cooling fan can also include additional rings arranged concentrically with the first ring. The additional rings may be spaced to prevent objects from contacting distal portions of the fan blades.

[0012] According to a second aspect, a cooling fan includes a hub and a plurality of blades extending radially outward from the hub. One or more of the blades can have axially spaced ribs extending from suction sides of the blades. The spacing between a first rib and the hub may be less than about 12 millimeters. The spacing between adjacent ribs may also be less than about 12 millimeters.

[0013] According to the second aspect, the ribs deflect objects before they contact the leading edges of the blades. The ribs may be constructed as part of the cooling fan by a molding process. The ribs do not add undue cost to a product including the cooling fan or occupy a large space in a chassis. In addition, the power of the motor turning the cooling fan does not need to be reduced. Therefore, smaller cooling fans can be used.

[0014] The above aspects and other aspects of the invention will be discussed with reference to the figures and to the detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE FIGURES

[0015]FIG. 1 is a perspective view of a suction side of a cooling fan according to a first embodiment of the invention.

[0016]FIG. 2 is an enlarged cut away view of a portion of the cooling fan illustrated by FIG. 1.

[0017]FIG. 3 is a perspective view of a pressure side of the cooling fan illustrated by FIG. 1.

[0018]FIG. 4 is a sectional view taken along line 4-4 in FIG. 2.

[0019]FIG. 5 is a perspective view of a suction side of a cooling fan according to a second embodiment of the invention.

[0020]FIG. 6 is a perspective view of a pressure side of the cooling fan illustrated by FIG. 5.

[0021]FIG. 7 is a sectional view taken along line 7-7 in FIG. 5.

[0022]FIG. 8 is a perspective view of a cooling fan according to a third embodiment of the invention.

[0023]FIG. 9 is a sectional view of a blade of the cooling fan illustrated by FIG. 8.

[0024]FIG. 10 is a plan view of a cooling fan according to a fourth embodiment of the present invention.

[0025]FIG. 11 is a perspective view of a cooling fan according to a fifth embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] A cooling fan according to the present invention will be described below by way of preferred embodiments and with reference to the accompanying drawings.

[0027]FIG. 1 is a perspective view of a cooling fan 100 according to a first embodiment of the invention. The cooling fan 100 has a suction side 102, which is upstream in a cooling airflow, and a pressure side 104, which is downstream in the cooling airflow. During operation, the cooling fan 100 rotates in the direction of the arrow, and moves air from the suction side 102 to the pressure side 104. The cooling fan 100 includes a hub 110 and a plurality of blades 112 extending radially outwardly from the hub 110. A first ring 120 is spaced from the hub 110 and intersects the blades 112. A second ring 122 is spaced from the first ring 120 and intersects the blades 112 at the tips of the blades 112.

[0028]FIG. 2 is an enlarged cut away view of a portion of the cooling fan 100. As illustrated by FIG. 2, the first ring 120 is spaced a distance d from the hub 110. The second ring 122 is spaced a distance d from the first ring 120. The first and second rings 120, 122 deflect objects away from the cooling fan 100 before being struck by the fan blades 112. The distance d may be chosen so that the cooling fan 100 complies with IEC/UL/UN 60950. Exemplary spacing values d are discussed below with reference to FIGS. 2 and 4.

[0029]FIG. 3 is a perspective view of the pressure side 104 of the cooling fan 100. FIG. 4 is a sectional view taken along line 4-4 in FIG. 2, and illustrates the arrangement of a blade 112 and the first ring 120. The first ring 120 extends outward from a suction side of the blade 112 by a distance t1. The first ring 120 also extends from the trailing edge 114 of the blade 112 by a distance t₂.

[0030] Referring to FIGS. 2 and 4, the distances d and t₁ may be selected so that the cooling fan 100 complies with IEC/UL/UN 60950. In general, a small distance t₁ means that the spacing d should also be relatively small. Conversely, a larger distance t₁ allows for a larger spacing d. One possible embodiment of the cooling fan 100 includes a spacing d of less than about 12 mm, and a distance t₁ of at least about 20 mm. Another possible embodiment includes a spacing d of about 5 mm, and a distance t₁ of about 1.5 mm. Other spacings d may be used. For example, for a spacing d of 8 mm, the distance t₁ should be at least about 9.3 mm. For a spacing d of 10 mm, the distance t₁ should be at least about 17.3 mm. In the embodiment illustrated by FIG. 1, the spacing d is between about 5 and 8 mm.

[0031] In FIG. 2, the spacing d is illustrated as present between the hub 110 and the first ring 120, and between the first ring 120 and the second ring 122. These respective spacings d and distances t₁ need not be identical, so long as each of the respective spacings d and distances t₁ comply with a selected safety standard.

[0032]FIG. 5 is a perspective view of a suction side 302 of a cooling fan 300 according to a second embodiment of the invention. A pressure side 304 of the cooling fan 300 is illustrated in FIG. 6. The cooling fan 300 has a hub 310 and a plurality of blades 312 extending radially outward from the hub 310. A first ring 320 is spaced from the hub 310, and a second ring 322 is spaced from the first ring 320.

[0033]FIG. 7 is a sectional view taken along line 7-7 in FIG. 5. A pressure side of the first ring 320 is connected to a suction side of the blades 312, and does not extend across the entire cross-section of the blades 312. The embodiment illustrated by FIGS. 5-7 is particularly desirable when the cooling fan 300 is only accessible from the suction side 302. In that case, there is no need to provide a deflection surface on the pressure side 304 of the cooling fan 300.

[0034] As in the case of the cooling fan 100 illustrated by FIGS. 1-4, the cooling fan 300 may be constructed to comply with IEC/UL/UN 60950. For example, the first ring 320 may be spaced from the hub 310 a spacing d (not illustrated), and the distance t₁ may be varied to account for differing values of d. The second ring 322 may also be spaced from the first ring by a distance d (not illustrated) and may extend outward from the blades 312 by a distance t₁. The spacing d and the distance t₁ may fall within the range of values used in the embodiment illustrated by FIGS. 1-4.

[0035] The embodiments illustrated by FIGS. 1-6 each include two rings to prevent objects from being struck by fan blades. It is within the scope of the invention, however, to include three or more rings. Additional rings may be included, for example, if the lengths of the blades are such that additional rings are needed to ensure a small enough spacing d to prevent contact with the blades. In addition, the second ring need not intersect the tips of the blades of the embodiments shown in FIGS. 1-6. For example, if the cooling fans 100 or 300 are to be mounted within a shroud, the blade tips may extend beyond an outermost ring of the fans 100, 300, contact with the blade tips being prevented by the shroud.

[0036]FIG. 8 is a perspective view of a cooling fan 500 according to a third embodiment of the invention. The cooling fan 500 has a suction side 502 and a pressure side 504, and includes a hub 510 and a plurality of blades 512 extending radially outward from the hub 510. In the embodiment illustrated by FIG. 8, each blade includes a first rib 520 and a second rib 522. The first and second ribs 520, 522 of the blades 512 provide a blunt upper surface that deflects objects away before they are struck by the blades 512.

[0037]FIG. 9 illustrates a sectional view of a blade 512 and the structure of a second rib 522. The second rib 522 includes a raised portion 524 having a blunt, rounded surface that deflect objects away from the blade 512 before being struck by a leading edge 516 of the blade 512. The second rib 522 can extend from a trailing edge 518, across the airfoil section 514, to the leading edge 516. The first and second ribs 520, 522 extend substantially along a circumferential direction of the cooling fan 500.

[0038] The distance d that the first rib 520 is spaced from the hub 510, and the distance t₁ that the first rib 520 extends past a suction side of the blades 712 may fall within the range of values used in the embodiment illustrated by FIGS. 1-4. The second rib 522 may also be spaced a distance d from the first rib 520, and extend a distance t₁ from a suction side of the blade 512.

[0039] In the third embodiment, the blades 512 have free ends. However, a third rib may be placed at the very tip end of each blade 512 to reduce the likelihood of an object being struck by the tips of the blades 512. If the cooling fan 500 is to be mounted within a shroud, a rib may not be necessary for the tips of the blades 512.

[0040] The embodiment illustrated by FIG. 8 includes first and second ribs 520, 522, however, a greater or fewer number of ribs may be included, depending on the length that the blades 512 extend in the radial direction.

[0041] In FIG. 8, each blade 512 includes first and second ribs 520, 522. The ribs may be, however, located on selected ones of the blades 512. For example, ribs can be placed on alternating blades 512. If the cooling fan 500 is rotated at a sufficient angular rate, the ribs would still serve to deflect an object away before being struck by a leading edge 516.

[0042]FIG. 10 is a plan view of a cooling fan 700 according to a fourth embodiment of the present invention. The cooling fan 700 includes a hub 710, blades 712 extending radially outward from the hub 710, a first ring 720 spaced from the hub 710, a second ring 722 spaced from the first ring 720, and a third ring 724 spaced from the second ring 722. The rings 720, 722, 724 may extend a distance t₁ (not illustrated) past suction sides of the blades 712. The distances t₁ and the spacings d may fall within the range of values used in the embodiment illustrated by FIGS. 1-4.

[0043]FIG. 11 illustrates a cooling fan 900 according to a fifth embodiment of the invention. The cooling fan 900 includes a hub 910 with blades 912 extending radially outward from the hub 910. The cooling fan 900 includes an inner ring 920, with tips 914 of the blades 912 being free. The cooling fan 900 may be mounted within a shroud, the shroud preventing access to the free tips 914. The cooling fan 900 may include distances t₁ and spacings d as in the embodiment illustrated by FIG. 1.

[0044] The cooling fan embodiments discussed above may be formed by, for example, molding a fan as a single element. The cooling fans may also be formed by joining separate elements to form a fan. The cooling fans can be made from, for example, plastics.

[0045] While the present invention is described with reference to exemplary embodiments, it will be understood that many modifications will be readily apparent to those skilled in the art, and the present disclosure is intended to cover variations thereof. 

What is claimed is:
 1. A cooling fan having a pressure side and a suction side, comprising: a hub; a plurality of blades extending radially outward from the hub; and a first ring spaced from the hub and intersecting the plurality of blades, wherein a spacing between the hub and the first ring is less than about 12 mm.
 2. The cooling fan of claim 1, comprising: a second ring spaced from the first ring and intersecting the plurality of blades, wherein a spacing between the first ring and the second ring is less than about 12 mm.
 3. The cooling fan of claim 2, wherein the first ring and the second ring extend outward from suction sides of the blades.
 4. The cooling fan of claim 3, wherein the first ring and the second ring extend outward at least about 1.5 mm from the suction sides of the blades.
 5. The cooling fan of claim 4, wherein the first ring is spaced from the hub a distance of between about 5 and 8 mm.
 6. The cooling fan of claim 5, wherein the second ring intersects the blades at tips of the blades.
 7. The cooling fan of claim 6, wherein the cooling fan is formed by molding.
 8. The cooling fan of claim 2, comprising: a third ring spaced from the second ring and intersecting the plurality of blades, wherein the spacing between the second ring and the third ring is less than about 12 mm.
 9. The cooling fan of claim 1, wherein a pressure side of the first ring is connected to a suction side of the blades.
 10. The cooling fan of claim 9, wherein the first ring extends outward from suction sides of the blades at least about 1.5 mm from the suction sides of the blades.
 11. The cooling fan of claim 1, wherein the first ring extends outward from suction sides of the blades at least about 1.5 mm from the suction sides of the blades.
 12. The cooling fan of claim 11, wherein the first ring is spaced from the hub a distance of between about 5 and 8 mm.
 13. The cooling fan of claim 1, wherein tips of the blades are free.
 14. A cooling fan having a pressure side and a suction side, comprising: a hub; and a plurality of blades extending outward from the hub, at least one blade including: a first rib spaced from the hub and extending outward from a suction side of the blade, wherein the spacing between the hub and the first rib is less than about 12 mm; and a second rib spaced from the first rib and extending outwardly from a suction side of the blade, wherein the spacing between the first rib and the second rib is less than about 12 mm.
 15. The cooling fan of claim 14, wherein the first and second ribs each include a raised portion extending outward from a suction side of the at least one blade.
 16. The cooling fan of claim 15, wherein the raised portions extend at least about 1.5 mm above the suction side of the at least one blade.
 17. The cooling fan of claim 16, wherein the first rib is spaced from the hub a distance of between about 5 and 8 mm.
 18. The cooling fan of claim 17, wherein the at least one blade comprises at least half of the plurality of blades.
 19. The cooling fan of claim 14, wherein the first and second ribs extend substantially along a circumferential direction of the cooling fan.
 20. The cooling fan of claim 14, wherein the cooling fan is formed by molding process. 